1. Field of the Invention
The present invention relates to a power-dividing device of a working vehicle that is formed to be able to divide or split a driving power input from a driving source into at least two routes.
The invention also relates to an axle-driving device for independently driving drive wheels with motor units provided for the respective drive axles.
2. Related Art
Conventionally, various power transmission structures in working vehicles have been proposed and employed. For example, there is a conventionally known structure in a working vehicle including a pump unit operatively connected to a driving source and a driven-side actuator fluid-connected to the pump unit, in which the actuator is disposed at a distance from the hydraulic pump.
In this structure, the hydraulic pump unit forms a main power transmission path for changing a speed of and outputting a driving power from the driving source together with the actuator.
Depending on uses, an auxiliary power transmission path may be required in some cases in addition to the main power transmission path in the power transmission structure including the hydraulic pump unit and the actuator disposed at a distance from each other. An example of these cases is a lawn mower in which power from a common driving source is divided or split and output into a traveling power transmission path for driving drive wheels and a PTO power transmission path for driving a work machine such as a mower.
Cases using a hydraulic motor unit as the actuator will be described below as examples.
There are disclosed, in U.S. Pat. No. 4,395,865 (hereafter, referred to as a cited reference 1) and U.S. Pat. No. 5,809,756 (hereafter, referred to as a cited reference 2), lawn mowers each including a PTO power transmission path for transmitting power from an engine to a mower in addition to a traveling power transmission path formed of a hydraulic pump unit operatively connected to the engine and a hydraulic motor unit disposed at a distance from the hydraulic pump unit to drive wheels.
More specifically, in the lawn mower described in the cited reference 1, first and second output shafts are provided to the engine as a common driving source and are operatively connected to the hydraulic pump unit and the mower, respectively. In other words, in the lawn mower described in the cited reference 1, the traveling power transmission path and the PTO power transmission path are completely separate from each other.
However, because the traveling power transmission path and the PTO power transmission path are completely separate from each other in this structure, the number of parts forming the power transmission paths increases and, also, large space for accommodating both the power transmission paths is required.
Moreover, in such a power transmission structure having the two power transmission paths, power transmission/interruption in each power transmission path needs to be independently controlled.
In this regard, electromagnetic clutches for power transmission/interruption are inserted into the respective power transmission paths in the lawn mower described in the cited reference 1, but there is a problem in that the electromagnetic clutches are of poor durability and, as a result, impair reliability of the power transmission paths.
On the other hand, in the lawn mower described in the cited reference 2, a common output shaft is provided to the engine and a pulley for the drive wheels and a pulley for the mower are supported on the common output shaft to thereby divide or split power from the common output shaft into the traveling power transmission path and the PTO power transmission path.
In this structure, however, there is a problem in that the common output shaft has to be made long and a large load is applied to the common output shaft.
Further, there is no description of how to transmit/interrupt power in the respective power transmission paths in the cited reference 2.
There are also conventionally known axle-driving devices in each of which a motor unit forming a non-stepwisely changeable transmission such as a hydrostatic transmission (hereafter, referred to as a HST) in cooperation with a drive-side actuator is provided to each a drive axle.
The conventional axle-driving devices will be described by taking cases, as examples, each using a hydraulic pump unit as the drive-side actuator and a hydraulic motor unit fluid-connected to the hydraulic pump unit as the motor unit.
Each of the axle-driving devices described in U.S. Pat. No. 4,920,733 (hereafter, referred as cited reference 3) and Japanese Utility Model Unexamined Publication No. 56-77437 (hereafter, referred as a cited reference 4) has an advantage that a cornering ability and, especially, an ability to make a small turn of a vehicle can be improved because the respective drive axles can be independently driven at changeable speeds. However, they are susceptible to improvement with regard to miniaturization of the whole units.
Especially, it is preferable to provide a brake unit to each drive axle so as to enable the vehicle to make a smaller turn. However, neither of the cited references mentions the brake unit and, of course, there is no description of miniaturization of the whole unit including the brake unit.
The present invention has been accomplished in view of the above related art, and it is an object of the invention to provide a power-dividing device of a working vehicle, that is capable of dividing or splitting a driving power input from a driving source into a main power transmission path including a pump unit and an auxiliary power transmission path including a PTO unit with a simple structure.
The present invention has been accomplished in view of the above related art, and it is another object of the invention to miniaturize a whole unit in the axle-driving device having a motor unit and a brake unit for each drive axle.
It is still another object of the invention to secure large and free space between drive wheels without increasing a distance between the drive wheels in a vehicle including the axle-driving device having the motor unit and the brake unit for each drive axle.